The present invention relates to an improved system and method for preventing condensate drain pan flooding using a liquid biocide or other liquid line cleaning solution (also collectively to be considered as “clog-clearing liquid”) dispersion to prevent clogging due to biological formation in either the condensate drain pan or the condensate drain line, and for detecting condensate water overflow and shutting the heat pump or air conditioner off to prevent further flooding in the event drain lines become plugged for any reason.
Biocide tablets or chemical line cleaning solution such as those discussed in U.S. Pat. No. 6,303,039 are commonly placed into a condensate drain pan or in a tablet dispenser. For example, U.S. Pat. No. 7,740,025 describes locating the tablets in the condensate drain line where they dissolve and prevent biological formation. Unfortunately, these tablets typically dissolve far too quickly, having been totally dissolved in hours or days but certainly not lasting weeks or months. Furthermore, even if the tables dissolve slowly over a period of months, the concentration of the biocide in the tablets typically will be too dilute to provide a desired biocide disinfection unless the biocide tablets when first used were impractically large. Another issue with biocide tablets is that they must be secured or weighted to prevent them from flowing into the flow path and restricting the condensate flow to the point of plugging the drain flow path.
Ideally a biocide or other line cleaning treatment, should last a minimum of the air conditioning season. An even better result would be a tablet that can last for a year, that is typically until the next annual AC check-up. It is also far better to locate the biocide treatment, such as a biocide tablet, in the condensate pan, rather than the condensate line because location of the biocide tablet in the pan allows both the pan and the lines to be treated for biological growth. Furthermore, biological growth in the pan means that potentially harmful biological allergens are continuously exposed to the conditioned air flowing in the house.
Although placing the biocide directly into the drain pan rather than the drain line is clearly preferred, a homeowner may not be willing or capable of unscrewing and opening a sheet metal panel of the air conditioner to place a tablet into the pan at some common interval, e.g. monthly.
It is well also known in the art to place a float switch in at least one of the condensate pan, the condensate drain line, the condensate overflow port, or a secondary containing pan and/or to place a moisture indicating switch in at least one of the condensate overflow port, secondary containing pan or the floor under the air handler of the air conditioner to assure that the air conditioner or the compressor of the air conditioner is deactivated should the condensate water back up and activate one of these types of alarm switches due to a failure of the condensate to properly drain. The float switch is typically a magnetic reed switch surrounded by a magnet in a float, configured so that once the liquid level rises the reed switch opens and the low-voltage circuit controlling the power to the entire air conditioner or the power to the compressor is opened. The moisture indicating switch is typically a form of electrical conductivity probe where electrically conductivity between electrodes indicates the presence of water across the probes, and then low-voltage circuit is opened to deactivate the air conditioning system. Either way, these switches are used to stop the cooling action of the air conditioner and thereby prevent the formation of additional condensate as well as prevent any flooding or additional flooding. One such float switch is the “SAFE-T-Switch” (http://www.rectorseal.com/safe-t-switch-model-ss2/) manufactured by Rectorseal (Houston, Tex.).
There are some disadvantages to the use of such float switches. For example; biological growth sometimes impedes the switch's free movement so the float is restrained from floating and the unit is not shut off to prevent an overflow. The movement of the float which is necessary to open the switch occasionally exceeds the pan height or the float is improperly adjusted, with the result that the water overflows before the float rises sufficiently to turn the unit off. This is, of course, the reason why a secondary float switch is used and is mandatory in some jurisdictions.
A conductivity detecting circuit, referred to as a moisture or water indicating switch or water-detecting switch, has been employed in which the presence of water across two electrodes completes a circuit and shuts off the air conditioner or compressor. Although mounting of a float switch is typically more involved than that of such circuits, the challenge with the latter, however, is to provide a device that is as cost competitive as a conventional float switch.
A secondary float switch is sometimes located in a secondary pan under the air handler. This configuration can be impractical where the air handler flow direction is upwards from below, making it difficult to place a secondary pan in this air flow path to catch any overflow of water. In those cases, a moisture- or water-indicating sensor is commonly used. This type of sensor is activated by the presence of water and is typically located on the on the floor either below or adjacent to the air conditioner's air handler like the conductivity detecting circuit previously discussed. The moisture or water indicating sensor serves as a back-up technique to detect any condensate water that might be leaking out of the air conditioner. They are typically some form of a conductivity sensor surrounded by a wicking material to accumulate the water around the two electrodes of the conductivity sensor. One such water detecting switch is the Wet Switch® which is manufactured by Diversitech (Duluth, Ga.) described on its website (http://media.diversitech.com/doc/DOC00015.pdf) as a solid state device designed to detect the presence of condensate water overflow.
A first object of the present invention is to provide a low-cost way to dispense a periodic shock loading and/or an intermittent or continuous preventative dosage of a biocide or other liquid line cleaning solution into the vapor compression system, where the quantity of liquid cleaning solution being dispensed can be optionally adjusted when a blockage is detected.
A second object of the present invention is to provide a low-cost way to provide an accurate and controlled release of biocide or other liquid line cleaning solution into the vapor compression system.
A third another object of the present invention is to provide a method of releasing the biocide or other liquid line cleaning solution into the vapor compression system at a time when dilution of the cleaning solution by the condensate flow will be minimized, such as when the air conditioner's cooling operation is just beginning.
A fourth object of the present invention is to combine a high condensate alarm, secondary water overflow alarm and anti-clogging biocide or other liquid line cleaning solution dispersion into a single electronic device to reduce cost and simplify installation.
A fifth object of the present invention is to provide a system that will advantageously deliver the biocide directly by any route to the condensate pan such as through the main condensate drain line, the overflow drain line, or other simple ingress path to the condensate pan like a drilled hole. While our currently preferred approach is to deliver the biocide through the drain line, one skilled in the art with the benefit of our teachings would now understand that numerous piping connections could be used to route the flowing liquid condensate to the drain pan without significant or costly modifications to the air handler within the scope of our invention.
A sixth object of the present invention is to automatically prevent biological formation and protection, for extended periods of time without user intervention, thereby eliminating the need to repeatedly place any biocide or other liquid line cleaning solution product in the drain line, in an in-line dispenser, or directly in the condensate pan and without the need to remove any panels on the unit.
A seventh object of the present invention is to provide a variable and adjustable quantity dispersion method for the biocide or other liquid line cleaning solution chemical such that a lethal concentration is provided when needed as determined by the status of the overflow protection sensor, lower dosages are dispersed for preventative purposes and no biocide is dispersed at other times.
An eight object of the present invention is to integrate the liquid line cleaning solution dispersion with primary condensate overflow protection using a singular connection to the drain pain, using either the secondary overflow connection or the primary flow connection.
A ninth object of the present invention is to integrate secondary condensate overflow protection into the device using one of a sensor in the secondary overflow connection, in the secondary drain pan or on the floor surface below the air conditioner.
A tenth object of the present invention is to prevent false alarms of water overflow, such as condensate, from unnecessarily halting the cooling operation of the air conditioner or the humidifier.
An eleventh object of the present invention is to use the injection of the biocide or other liquid line cleaning solution, when an overflow condition is detected, in an effort to clear a clogged flow path. We have recognized that if both secondary and primary overflow are monitored separately and the primary overflow sensor has detected water, then in addition to stopping operation of the unit, the injection of clog clearing solution is continued for an additional dose of cleaner up to a maximum dosage which is determined by the detection of moisture at the secondary overflow sensor. Use of the secondary sensor to detect overflow will maximize the quantity of clog-clearing cleaner used and increase the likelihood of clearing any clog in the flow path while keeping the unit from producing additional condensate since the unit is off. With no additional condensate being generated, the biocide is not further diluted.
A twelfth object of the present invention is to monitor for the overflow of the air conditioner condensate drain system and/or the heating or humidifier system. The present invention allows any desired number of low-cost additional conductivity sensors to be placed in overflow locations of the heating and/or cooling systems, all wired in parallel, to shut off either humidification operation during heating season and/or cooling operation, and to dose additional biocide or other liquid line cleaning solution if water is detected.
A thirteenth object of the present invention is to prevent false alarms caused by moisture or water droplets bridging the moisture detecting electrodes, namely that condensate overflow is being detected at the sensor location. One method to achieve this object is to use more than two conductivity electrodes (wired in series or monitored separately), a second method is to provide a more tortuous path for the liquid water to reach one or more of the electrodes, and a third method is to exploit the differential pressure that exists between the drain pan and the interior of the home to flow air over one or more electrodes to prevent the accumulation of moisture on the electrodes that could result in false alarms.